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T/F: corona dominating for LV lines

Short answer

FALSE. Corona inception voltage is far above LV line voltages, so corona is negligible. It becomes a design constraint only for EHV/UHV lines (≥220 kV), while LV lines are governed by voltage drop and thermal limits.

State and justify whether the following statement is TRUE or FALSE: Corona is more dominating design criterion for LV transmission lines.

FALSE.

Corona starts when the phase voltage exceeds the disruptive critical voltage

Vd=21.1 m0 δ rln⁡Dr kVV_d = 21.1\,m_0\,\delta\,r\ln\frac{D}{r}\ \text{kV}
  • On LV and MV lines (up to 33 kV), the operating voltage is far below VdV_d even for small conductors. For example, a 10 mm conductor at 1 m spacing has Vd≈21.1×0.85×0.5ln⁡(200)≈47.5V_d \approx 21.1 \times 0.85 \times 0.5\ln(200) \approx 47.5 kV per phase, which is well above 33 kV/3\sqrt{3}. So corona is practically absent.
  • Corona becomes a governing design criterion only for EHV/UHV lines (220 kV and above). There it sets:
    • the minimum conductor diameter,
    • the use of bundled conductors (400 kV and above),
    • limits on radio interference and audible noise.

LV line design is governed instead by voltage drop, current-carrying capacity and mechanical strength.

✓ Answer checked by Claude Opus 5.5 (high effort)

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